The long range objective is to evaluate the possible use of human lymphocytes as potential markers of human exposure an susceptibility. The relationship between chemical exposure and changes in biochemical or cytogenetic parameters will be investigated in both defined human populations and animal models. The effect of pharmacokinetic parameters of activation/deactivation on the generation of biologically effective doses (i.e., DNA adducts) and the resulting consequences on biological endpoints such as SCEs and DNA damage will be evaluated in human lymphocytes following in vitro exposure to chemicals. A study was undertaken to (1) determine the role of metabolic activation-deactivation pathways on DNA adduct formation and SCE induction by incubating lymphocytes in vitro with benzo(a)pyrene (BP) and (2) determine whether smoking exposure resulted in smoking-related adducts which could be measured in lymphocytes by 32P-postlabelling methods. Endpoints studied included BP-BNA adduct formation, BP metabolism, ethoxyresorufin-O-deethylase (EROD) activity, glutathione-S- transferase (G-ST) activity and SCE induction. We showed that in bitro BP metabolism, EROD activity, SCE induction by BP or BPDE-dG adduct levels did not differ between smokers and nonsmokers. However, we did observe a large inter-individual variation for these endpoints. We found that the correlation between lymphocyte BP metabolism and DNA adduct formation was weak for the whole population, however when the population was segregated on the basis of G-ST activity (deactivation pathway for reactive epoxides) there was a very strong correlation between BP metabolism and DNA adduct formation for persons with high G-ST activity. Individuals with low activity showed a very weak correlation. 32P-postlabelling of human lymphocytes resulted in the detection of several DNA-adduct spots which varied considerably among individuals. However none appeared to be smoking related. Future studies will determine the role of G-ST activity and whether there is a correlation between endogenous adduct levels and a persons capacity to metabolize chemicals to DNA reactive species following in vitro exposure.